«إن كان موجودا في الخارج»
If the subject exists outside the mind.
A categorical judgment considered with reference to an externally existing subject is called external (khārijiyyah). “External” distinguishes actual existence from a merely mental concept.
«الإنسان كاتب»
A human is a writer.
The book uses this to illustrate consideration of humans as externally existing. This does not establish that every human actually writes; the proposition’s quantity and factual truth are separate matters.